The present invention relates to therapeutic orthopedic devices for fixating, immobilizing, and manipulating the human anatomical skeleton, particularly the foot and lower leg. And, more specifically, the present invention relates to external frame systems and devices for fixating lower leg bones and the foot with respect to the tibia.
External Fixation devices locate segments of bone relative to a reference location of the skeleton for varied purposes including reconstruction of fractured or deformed extremities. By distracting or compressing portions of the anatomical skeleton, external fixation devices can correct angulation, rotation, and translation of targeted bones or bone segments.
External fixation—an orthopedic procedure utilizing external fixation devices—involves surgically securing bone pins both above and below a bone fracture or chosen site for manipulation, providing attachment points that may couple with or to another component, such as a clamp or frame member, of the external fixation system.
One particular form of external fixation, circular fixation (also called external ring fixation), is a proven medical treatment technique to overcome, correct, or repair many problems of the lower leg and foot stemming from traumatic injuries, infections, non-unions, or congenital abnormalities.
One drawback of circular fixation treatments includes a lengthy treatment duration—often in excess of one year—during which the patient's foot and lower leg are immobilized in a cumbersome external fixation structure consisting of varied components including pins, wires, support rods, clamps, and frames. This duration of immobilization is necessary for precise manipulation and to permit bone regrowth.
Another drawback of existing circular fixation treatments and systems is that patients have restricted movement. This restriction is a result of the quantity and placement of cumbersome components that—due to their size, weight, and anatomic placement—severely restrict and impair motion to a range that is far less than the patient's accustomed normal range.
Yet these components, despite their size and weight, are vital to ensure proper treatment. External fixation can practically manipulate bone in any desired combination of translation, rotation, angle, or length. When applied to the foot and lower leg, external fixation treatments include the use of structures incorporating one or more external ring frame members (semi-circumferential or full circumferential frame members) to encompass and stabilize the limb by pins and or tensioned wires. The circular frames are employed to capitalize on these biologic phenomenae that govern tissue (in particular, bone) growth under tension and optimized distraction rates.
Bone regrowth as a result of circular fixation applies an accepted treatment termed controlled distraction histogenesis, whereby bone is fractured and then slowly lengthened at a very specific and controlled rate to optimize bone regrowth. As the fractured bone is distracted, new bone growth occurs in the fracture region and establishes a new segment of healthy bone in the defect. The tension that is created by gradual distraction stimulates the formation of new bone, skin, blood vessels, peripheral nerves, and muscle. Circular fixation thus allows for an external means of manipulating translational, rotational, angular, and even length discrepancies while preserving soft tissue from excessive trauma that would otherwise prevent early motion and use of the limb.
However, existing circular external fixation systems inadequately address the patient's desire and need to use the constricted limb as close to normal as possible. Specifically, existing external fixation systems inadequately address the patient's need for an ambulatory load-bearing construct that enables or approximates the patient's normal (unencumbered) gait. Existing solutions that attempt to address this patient need range from surgeon prescribed, makeshift devices to utilizing a second foot ring placed below the foot to provide rudimentary, albeit sub-optimal, support. Although these solutions provide a “contact” platform under the foot, they fail to provide adequate cushioning, adjustability [for gait], and removability, or any combination of these characteristics.
And, more problematic, injuries and other abnormities of the foot require additional frame elements including a foot ring. A foot ring is mounted to the foot with pins and/or tensioned wires in the same manner as rings above the ankle are attached to the tibia. Foot rings can be difficult to align and mount either because of more challenging deformities of the foot such as equinus contractures or varus deformities, or simply because of the difficulty surgeons encounter when trying to manually align the foot ring properly with the foot. Often the result is an attached foot ring that is non-plantigrade, or poorly aligned with the horizontal axis of the foot. As a result, the patient often cannot load-bear due to hardware attachments beneath the foot ring, the position of the foot ring, the position of the foot ring relative to the foot, or because of a pre-existing anatomic position that prohibits them from walking normally.
In an attempt to provide adequate clearance for an inferior encumbrance, patients often have an additional ring, or footplate, attached beneath their foot that allows them to bear weight and, using crutches, ambulate. This additional ring or foot ring attaches with four (or more) threaded rods that are secured with multiple nuts above and below each ring. This requires both precise location in a clinical or surgical setting and tools including wenches.
Additionally, many prior-art foot rings, or foot-ring walking attachments, do not provide any cushioning or traction-enhancing features. So, in an attempt to provide patients with more comfort, some orthopedists have crudely attached materials with a walking, rubberized tread to the bottom of the additional foot ring. These devices represent existing elements of systems whose intended use(s) were for different locations but have been implemented as makeshift adaptations for this function.
Known prior-art or state-of-the-art external fixations systems present additional drawbacks when applied for use as a walking attachment. Frame members that were not designed specifically as a footplate do not provide for the cushion or tread necessary for such a longitudinal course of treatment. Moreover, these devices are difficult to adjust to a patient's comfort given the planar variances of each patient's foot position and the need for the device to adapt to a wide spectrum of variation between individual patients.
Further, because the adjustments made to existing devices require tools (such as wrenches), to tighten and loosen nuts on threaded rods and on bolts, it can be very difficult, if not impossible for a patient to accurately adjust their ring for comfort or hygiene. Any comfort gain by removal for bathing or at bedtime is eclipsed by the arduousness of this task and, often for the entire duration of treatment, an individual patient will not remove their load-bearing ring.
Normal ambulation is further encumbered by additional length due to the height of the external fixation systems. This additional length causes an abnormal gait and further causes hip and knee problems.
One device that recognizes the need for a walking platform is the “rocker bottom” attachment manufactured by DePuy, Johnson & Johnson. This device enables a direct attachment to the underside of the patient's foot ring, and provides a “rocker” type bottom that is intended to promote and ease the forward motion of a patient as they bring their limb forward, touch down, and then “rock” forward. The deficiency of this device is multifold in that it nearly eliminates all available attachment points for wire fixation to the foot ring due to it's size and shape that mirrors the foot ring and, hence eclipses, all attachment point options. The DePuy device, because it attaches using multiple bolts and nuts, makes very difficult if not impossible for the patient to remove his device when bathing or sleeping. Finally, and most significantly, the DePuy device does not inherently provide a means for planar adjustability; there is no available means for either a surgeon or patient to easily adjust the position of their means for comfort, supplemental correction, or just ambulating.
Of course, a curved bottom portion is generally known in the art to aid walking for patients in controlled motion devices. For example, Crispin, in U.S. Pat. No. 4,771,768 issued on 20 Sep. 1988, describes the benefits of a rigid shell with a curved bottom to provide a rocking heel to toe motion of a patient's foot during weight bearing when encumbered in a motion control cast.
Other external fixation devices for the repair of the anatomical skeleton are known. One state-of-the-art representative device, hereby incorporated by reference as if fully set forth herein, includes the external fixation system described by Walulik et al. in U.S. Pat. No. 6,277,119 issued on 21 Aug. 2001. The Walulik device includes interchangeable and distinct components that allow for a greater degree of surgeon flexibility in producing a desired construction to secure bone portions with bone pins. These components include at least one cylindrical support rod and a plurality of universal clamp assemblies for engagement with at least one support rod.
Specialized external fixation systems that enable a patient to bear weight on the fixed lower extremity are also generally known. Such specialized systems enable the gradual increase of the patient's own weight on the immobilized limb to hasten recovery and promote tissue and bone regeneration. One representative example of such specialized lower-extremity external fixation systems include the combination bone fixation/immobilization apparatus of Grant et al., described in U.S. Pat. No. 6,964,663 issued on 15 Nov. 2005 and this disclosure is hereby incorporated by reference as if fully set forth herein limb. The Grant device includes a walking attachment adapted to have a plurality of transfixation wires fixed thereto and includes a substantially rigid leg support assembly comprising a cuff and strap.
Problems common to the current-state-of-the-art devices, represented above, include an unacceptable level of precision that must be maintained during the creation of the frame structure in orientating each component while a multitude of fasteners are tightened. Further, as many of the components interact with other components, manipulation or adjustment of one selected clamp, for instance, requires cooperating adjustments to several sub-systems and fasteners. Not only is such adjustments time-consuming, they are often impossible for the patient to make on their own because the patient is unable to reach the fasteners due to poor flexibility or simply because the location is out of the range of normal-human motion for a device worn on the foot. Moreover, the inter-dependent nature of the fasteners often require incremental adjustments made in sequence with each of the multiple fasteners, which requires a skill beyond the average patient.
Attempts to make external fixation systems more quickly and easily assembled and adjusted include the adjustable bone stabilizing frame system described by Wainquist et al. in U.S. Pat. No. 6,613,049 issued on 2 Sep. 2003. The Wainquist device includes clamping members with friction pins internally mounted in each clamp, which engages a rod-member once the rod is inserted into the jaws of the clamp.
Another external fixation system, described by Ferrante et al. in U.S. Pat. No. 7,048,735 issued on 23 May 2006 includes clamping elements that provide three-axes of rotation relative to the other capture member.
Despite the varied attempts at improving external frame fixation systems, many problems specific to the lower extremity and, particularly, to the foot, have not been adequately addressed. For example, patient comfort, gait, hygiene, ease of removal are inferior in known systems. Further, self adjustability by the patient, providing a flexing suspension to absorb shock from gait, providing a more normalized gait, reducing complexity, making a system more economical to produce, and reducing the number of components are all characteristics yet to be incorporated in known external frame fixation systems. Thus, there remains a need for an improved external ring fixation system particularly adapted for use with the foot that overcomes these aforementioned limitations.